TY - JOUR
T1 - Evidence of a role for modulated atmospheric tides in the dependence of sporadic E layers on planetary waves
AU - Pancheva, D
AU - Haldoupis, C
AU - Meek, C E
AU - Manson, A H
AU - Mitchell, N J
N1 - ID number: ISI:000183108300007
PY - 2003
Y1 - 2003
N2 - [1] A large amplitude, 7-day period westward propagating S = 1 planetary wave (PW) of global response has been reported from ground radar and satellite wind measurements in the mesosphere-lower thermosphere (MLT) during the second half of August and well into September 1993. Following recent suggestions that PW might play a role in the formation of midlatitude sporadic E layers (E-s), Haldoupis and Pancheva [2002] found a strong 7-day periodicity present in all stations concurrently with the 7-day planetary wave reported elsewhere, by analyzing sporadic E critical frequency (foEs) time series from eight midlatitude ionosonde stations covering a longitudinal zone from about 58 degreesE to 157 degreesW. This study provided the first direct proof in favor of a PW role on E-s formation. In the present paper we further investigate this role by considering the same PW event and correlating the 7-day periodicity in foEs directly with concurrent variations in the mesospheric neutral wind measured with atmospheric radars in Saskatoon, Canada, and in Sheffield, United Kingdom. Although our analysis cannot exclude a direct PW role on E-s formation, it shows clearly that E-s is affected indirectly by the PW through the action of the diurnal and semidiurnal tides which are strongly modulated by the same PW, apparently through a nonlinear interaction process at altitudes below 100 km. This 7-day PW modulation was found to be clearly present simultaneously in the amplitude of the zonal 12-hour tidal wind, the meridional 24-hour tidal wind, and in both, the 12-hour and 24-hour periodicities which existed in the foEs time series. The results here provide a new physical explanation for the observed relation between sporadic E layers and planetary waves.
AB - [1] A large amplitude, 7-day period westward propagating S = 1 planetary wave (PW) of global response has been reported from ground radar and satellite wind measurements in the mesosphere-lower thermosphere (MLT) during the second half of August and well into September 1993. Following recent suggestions that PW might play a role in the formation of midlatitude sporadic E layers (E-s), Haldoupis and Pancheva [2002] found a strong 7-day periodicity present in all stations concurrently with the 7-day planetary wave reported elsewhere, by analyzing sporadic E critical frequency (foEs) time series from eight midlatitude ionosonde stations covering a longitudinal zone from about 58 degreesE to 157 degreesW. This study provided the first direct proof in favor of a PW role on E-s formation. In the present paper we further investigate this role by considering the same PW event and correlating the 7-day periodicity in foEs directly with concurrent variations in the mesospheric neutral wind measured with atmospheric radars in Saskatoon, Canada, and in Sheffield, United Kingdom. Although our analysis cannot exclude a direct PW role on E-s formation, it shows clearly that E-s is affected indirectly by the PW through the action of the diurnal and semidiurnal tides which are strongly modulated by the same PW, apparently through a nonlinear interaction process at altitudes below 100 km. This 7-day PW modulation was found to be clearly present simultaneously in the amplitude of the zonal 12-hour tidal wind, the meridional 24-hour tidal wind, and in both, the 12-hour and 24-hour periodicities which existed in the foEs time series. The results here provide a new physical explanation for the observed relation between sporadic E layers and planetary waves.
U2 - 10.1029/2002ja009788
DO - 10.1029/2002ja009788
M3 - Article
SN - 0148-0227
VL - 108
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
IS - A5
ER -